Which counterexample shows that the conjecture "All animals that can fly are birds" is false?

It seems like you forgot to post the answer choices. However, bats are one animal where they can fly but they aren't birds. So this is one counter-example to prove the claim false. Another example would be any flying insects.

B would be incorrect as it is not a counterexample to the claim. C would be incorrect as a chipmunk is not a bird. And D would be incorrect as the claim says "All animals that can fly are birds" it doesn't say "every bird" or "all birds can fly"

So A is the logical choice and according to what Jimthompson5910 said "bats are one animal where they can fly but they aren't birds."